Method of constructing and laying street-pavements or roadways.



' NlTED STATES Patented M y 5, 190a.

PATENT OFFICE.

METHOD OF CONSTRUCTING AND LAYiNG STREET-PAVEMENTS OR ROADWAYS.

SPECIFICATION forming part of Letters Patent N 0. 727,509, dated May 5, 1903. Application filed January 13, 1902. Serial No. 89,542. No specimens.)

To all whom, it may concern:

Be it known that I, FREDERICK J. WARREN, a citizen of the United States, residing at Newton, in the county of Middlesex and State of Massachusetts, have invented a new and useful Improvement in Methods of Constructing and Laying Street-Pavements or Roadways, of which the following is a full, clear, and exact description.

Theinven tion relates especially to that part of a street-pavement or roadway which constitutes its upper course and which is the course which is adapted to receive the wear of trafldc and to cover and seal from atmospheric influences the foundation.

The object of the invention is to provide a street-pavement or roadway with a wearing course or section which shall consist of mineral (stony) elements or components of a character adapted to form in and of themselves a stable or solid support for traffic combined and united by a bituminous mastic of a predetermined volume, which volume is greater than that required to fill the cubical contents of the voids which would otherwise exist in the mineral base composed of said elements or components were they unfilled and which bituminous mastic and mineral elements or components are united under pressure in place on the foundation and produce a structure the wearing-surface of which is more largely mineral than bituminous mastic and which has the mineral elements so disposed therein as to support and sustain the bituminous mastic, while the bituminous mastic acts to unite the mineral elements or components, to partially sustain them, and to form with them a weatherproof and waterproof structure, in which the mineral elements largely preponderate throughout the mass.

In practicing the method such mineral elements or components are selected and proportioned as will provide without the aid of the bituminous mastic a compact, stable, or solid body of about the size of the complete section. or course of pavement. This should be of sufficient stability to reinforce the bituminous mastic and receive the principal part of the wear of traffic. The mineral components for this purpose may vary considerably in size from pieces as large as three inches in diameter to small particles or atoms.

The best result is secured by using components so varying in size that when associated they will tend in their associated form to eliminate voids to a very considerable extent, thereby, on the one hand, adding to the stability of the stony body and, on the other hand, requiring a smaller quantity of bituminous mastic for filling the interstices and uniting and holding the mineral components. It is obvious that this mineral body must be carefully prepared and proportioned. The mixture which I-prefer to use is composed of relatively coarse particles one-half to three inches in diameter, intermediate particles one-tenth to one-half inch in diameter, and fine particles from an impalpable powder to one-tenth inch in diameter suitably proportioned, graded, and thoroughly mixed. These ingredients are such as will pass through screens having a three-inch mesh, a one-halfinch mesh, one-tenth-inch mesh, one-fortiethinch mesh, one-eightieth-inch mesh, and one two-hundredth-inch mesh. Of the ingredients passing through a screen of three-inch mesh and remaining upon a screen of onehalf-inch mesh I take about seventy parts, of the ingredients passing through a screen of onehalf inch mesh and remainining upon a screen of one-tenth-inch meshItake about twenty parts, and about the same as to screens of one-tenth-inch mesh and one-fortiethinch mesh. I take about four parts of screens of one-fortieth-inch mesh and oneeightieth inch mesh, and three parts of screens of one-eightieth-inch mesh and one two-hundredth-inch mesh, and of material passing through a screen of one two-hundredth-inch mesh one part. I do not, however, confine myself to these sizes of ingredients or their proportions to each other indicated, as they both may vary within reason and still a dense body of mineral ingredients be obtained. These mineral components thus selected and proportioned are then treated with a quantity 01": fluid bituminous mastic of a Volume more than sufficient to till the voids throughout the stony body and in a manner to cause the mineral components to be coated with such bituminous mastic. The

proportion which the bituminous composition bears to the mineral ingredients will vary slightly as the percentage of voids in the 'perature of about 200.

mineral base may vary. As a rule, however, the proportion should be such as to permit the voids to be filled and also to further permit a slight thickening of the composition between the ingredients of the mineral base in order that they may not lie perfectly hard against each other. This will effect a slight thickening of the wearing-section throughout and also provides a cushioning etfect which is greater than that where a smaller percentage of bituminous com position is used. From eight to ten parts of the bituminous composition to the entire number of parts will accomplish this end. The mineral ingredients are carefully graded, thoroughly combined by mixing with each other, and coated with the bituminous composition while at a tem- The bituminous mastic-coated mineral components are then laid upon a suitably-prepared foundation and uniformly disposed thereon to form a level surface and then subjected to pressure, which has the effect of causing the bituminous mastic to flow into all the voids and interstices in the stony body to fill them and also cause the bituminous mastic to bear or press against the mineral components to such an extent that the whole mass or body constituting the said wearing section or course is somewhat thickened, the bituminous mastic by this thickening serving to form, as it were, an impervious matrix and binder for each mineral component without, however, depriving the mineral body of that compactness and stability which is necessary for enabling it to take the main part of the wear of traffic. The excess of bituminous mastic after this action has taken place covers the wearing-surface of the section with a thin coating or layer which smooths and finishes the upper surface, but which is not calculated to take wear, but only as a sealing medium.

The bituminous mastic which I employ may have any suitable composition. For some purposes I prefer bituminous mastic which contains more than the usual amount of dead oil, and is therefore in a more continuously-plastic condition for a long period of time than is the ordinary bituminous mastic.

The wearing-section of a pavement of the character which I have described having its stability dependent upon the mineral base rather than upon the bituminous mastic may include with advantage a softer bituminous mastic of this character, and such a bituminous mastic will give to the wearing-section a resiliency or flexibility which ordinary bituminous mastics will not provide, at least to so great an extent. A bituminous mastic of this character preserves for many years a relative softness or plasticity, which denotes life, and also contains adhesive properties of such great value that the mineral components of the base while united by such a bituminous mastic may still yield somewhat with respectto each other without opening the voids or fracturing or breaking the uniting mastic, the mastic in effect forming a resilient automatically-conformable impervious joint for the mineral components whichit holds. This quality in the wearing-section of a street-pavement or roadway is very valuable in that it means long life, ease to horses use and to travel, and freedom from noise and dust.

This pavement is a variation of my bituminous macadam invention, and it. varies from all previous pavements of which I have knowledge in respect to the sizes and proportions of the mineral ingredients used and in respect also to the manner in which the bituminous composition is combined with them to secure in a wearing-section the inherent stability arising from the inherent stability of the mineral ingredients and also an increased cushioning effect, which, however, does not militate against the inherent stability which it is necessary to always retain to provide the most lasting and satisfactory effects in this type of pavement.

Having thus fully described my invention, I claim and desire to secure by Letters Patent of the United States- 1. In a pavement, a mineral or wearing structure possessing inherent stability and a hinder or cement in excess of the amount sufficient to fill the voids in said structure, substantially as described.

2. In a pavement, a mineral or wearing structure possessing inherent stability and a binder or cement incorporated into thebody thereof in an amount more than sufficient to fill the voids naturally existing in said structure, substantially as described.

3. In a pavement, a mineral or wearing structure of inherent stability and a binder or cementso incorporated into the same as to not only till the voids naturally existing therein but to also provide a somewhat elastic medium between the abutting points of the ingredients.

4. In a pavement, a mineral or wearing structure possessing inherent stability and a binder or cement occupying the natural voids in such structure and also spaces between the opposing ingredients, substantially as described.

5. In a pavement, a structure composed of mineral or wearing ingredients of several grades so proportioned and mixed as to give the structure an inherent stability in combination with a binder or cement incorporated therein in such amounts as to occupy the natural voids in said structure and also spaces between the opposing ingredients.

6. In a pavement, a structure composed of mineral or Wearing ingredients of several grades so proportioned and mixed as to give the structure an inherent stability in combination with a cement or binder incorporated therein in amounts more than sufficient to fill the voids naturally existing in said structure.

7. In a pavement, a structure composed of mineral or wearing ingredients of several ICC grades the ingredients of one grade being so proportioned to the voids existingin the next larger grade as to give the structure an inherent stability and a binder incorporated in said structure in amounts more than sufiicient to fill its natural voids.

8. In a pavement, a mineral or Wearing structure of inherent stability having incorporated therein a compressed cement or binder of a volume more than su fficient to fill the voids naturally existing therein.

9. In a pavement, a mineral or wearing structure of inherent stability having incorporated therein a compressed asphaltio cementor binder of some resiliency or elasticity and of a volume more than sufficient after compression to fill the voids naturally existing in the aforesaid structure.

10. In a pavement, a mineral or wearing structure of inherent stability having incorporated therein a compressed cement or binder of some resiliency or elasticity and of a volume sufiicient to fill not only the voids naturally existing in the structure but to also form an intervening layer or cushion between the otherwise abutting points of the ingredients.

11. In a pavement, a structure composed of mineral or wearing ingredients of several grades, so proportioned and mixed as to give the structure an inherent stability and a compressed cement or binder incorporated therein in amounts more than sufficient to fill the voids naturally existing in said structure.

12. In a pavement, a structure composed of mineral or wearing ingredients of several grades being so proportioned and mixed with regard to the voids in the next larger grades as to give the structure an inherent stability in combination with a compressed cement or hinder of some resiliency or elasticity incorporated into the structure in amounts sufficient not only to fill the voids naturally existing in said structure but also to form a layer between the otherwise abutting points of the ingredients.

13. The method for producing a firm and elastic pavement from such mineral or wearing ingredients as have naturally an inherent stability consisting in coating such ingredients with a fluid or semifluid cement or binder and after applying the resulting mixture to the road-bed rolling with such considerable pressure as to reduce the thickness of the same and to closely compact the whole, compressing the cement or binder between the opposing ingredients.

14. The method of producing a firm and elastic pavement from such mineral or wearing ingredients as have naturally an inherent stability, consisting in mixing such ingredients with a fluid or semifluid hinder or cement in an amount in excess of the natural voids existing in the structure of said ingredients, and after laying, rolling with such pressure as to actually compress the cement.

15. The method of producing a firm and elastic pavement consisting in selecting mineral or Wearing ingredients of several grades, proportioning the ingredients of one grade to the voids existing in another grade and thoroughly mixing, then mixing with a volume of binder or cement sufficient not only to fill the voids naturally existing in the mineral structure but also to form a layer between the otherwise abutting points of the ingredients, then laying and rolling with such pressure as to compress the cement or binder and force the aforesaid abutting point-s'closer together though not into actual contact.

16. The method of producing a firm and elastic pavement consistingin selecting mineral or wearing ingredients of several grades, proportioning the ingredients of one grade to the voids of the next larger grade above, mixing the ingredients with a. fluid or semifluid cement or binder in quantities in excess of the voids existing in the mineral structure and then subjecting the whole to a pressure sufficiently great to compress the cement and force the ingredients closer together but not into actual contact.

17. A pavement composed of a mineral or wearing structure of inherent stability in combination with a binder or cement compressed below its normal volume incorporated in said structure and rendering the same elastic or resilient.

18. In a pavement, a structure composed of mineral or wearing ingredients of several grades, so proportioned as to give the structure an inherent stability and a cement or hinder uniting said ingredients and maintained in the structure in a state of compression below its normal volume, thereby rendering the structure elastic and resilient.

19. The method of constructing and laying the wearing course or section of a street sheet pavement or roadway consisting in selecting mineral elements or components of the sizes and proportions specified adapted to form in and of themselves a substantially stable or solid support for traffic of the required thickness, thoroughly coating thesurfaces of said elements or components with a bituminous mastic to an extent which shall cause the aggregate of bituminous mastic thus applied to exceed in volume that required to close the voids in the mineral base composed of said elements or components were they unfilled, then laying such coated mineral elements or components upon a prepared base and'to any thickness required and then subjecting the said coated components to action of pressure whereby the mastic coating is caused to densely fill the voids and somewhat thicken the entire wearing-section, the mineral elements tending to support and sustain the bituminous mastic and the bituminous mastic acting to unite the mineral elements or 'com-' ponents and form with them a weatherproof and waterproof structure the Wearing-surface of which is more largely mineral than bituminous mastic.

IIO

20. The method of constructing and laying a street sheet pavement or roadway comprising the employment and association of mineral ingredients varying as to size and as to their proportions substantially as herein indicated and adapted in and of themselves to form a base having inherent stability combined with a bituminous composition slightly in excess of that required to fill the voids in the base which would otherwise exist and combined with the mineral ingredients when in place in the pavement or roadway under pressure, whereby the voids, are filled and the mineral ingredients slightly separated from each other by thin cushioning and uniting films of the bituminous composition and a flexible jointure between them and an increased resiliency of the entire wearing-section obtained.

21. The Wearing course or section ofa street sheet pavement or roadway herein described, the same consisting of a mineral base comprising mineral elements or components of the sizes and proportions substantially herein indicated, uniformly mingled together, and forming a base possessing inherent stability in and of itself, and a bituminous composition of a quantity in excess of that required to fill the voids, which would otherwise exist I FREDERICK J. WARREN.

Witnesses:

F. F. RAYMOND, 2d, J. M. DOLAN. 

